KR970003771B1 - Reconstitutable nuclear fuel assembly having locking tubes with dimples - Google Patents

Abstract

No summary.

Description

Apparatus for removably attaching the upper nozzle of the reconfigurable fuel assembly to the upper end of the guide tumble

1 is a front view of a vertically shortened reconfigurable fuel assembly.

2 is an exploded cross-sectional view of the components of the attachment device of the present invention.

3 is an assembled cross-sectional view of the components of the attachment device shown in FIG.

4 is a plan view of the components making up the internal socket of the attachment device shown along arrow IV-IV in FIG.

5 is a partially enlarged view illustrating a state in which a dimple on the fixed tube maintains the fixed tube in a proper fixing position.

FIG. 6 is a side view of the reusable fixation tube shown along arrow VI-VI of FIG. 2. FIG.

FIG. 7 is a plan cross-sectional view of the cannula shown along arrow VII-VII of FIG. 6. FIG.

FIG. 8 is a plan sectional view of the cannula shown along arrows VIII-VIII of FIG.

* Description of the symbols for the main parts of the drawings *

10 fuel assembly 12 bottom nozzle

14: guide dimple 16: horizontal lattice

18: fuel rod 20: upper nozzle

22: adapter plate 24: fixed tube

26: outer socket 32: jaw

34: annular groove 36: internal socket

38: slot 40: finger

44: bulge 48: concave

58,62: Dimples 60,64: Tips

FIELD OF THE INVENTION The present invention generally relates to a reconfigurable fuel assembly for a reactor, and more particularly, to an apparatus for removably attaching an upper nozzle of a reconfigurable fuel assembly to a guide tumble.

In a typical reactor, the reactor core comprises a plurality of fuel assemblies, each fuel assembly having a top and bottom nozzle, a plurality of elongated guided dimples extending longitudinally at appropriate intervals between the nozzles, and a predetermined distance laterally. It consists of a number of transverse support grids attached to the guide table. In addition, each fuel assembly includes a guide dimple between the top and bottom nozzles and a plurality of elongated fuel rods supported by the transverse lattice at predetermined intervals transversely from the longitudinal. Fuel rods containing fissile material are grouped in a systematic arrangement to provide sufficient neutron flux to maintain high rates of fission in the core. The reactor has a control rod that can be inserted into the guide tumble to control fission reactions that release large amounts of energy in the form of heat. The liquid coolant flows upward through the core for the purpose of extracting some of the heat generated by the core to generate power.

When operating a reactor, fuel rods can sometimes cause cracks due to internal stress along their length. These defective fuel rods must be replaced in the fuel assembly, which must be made underwater because the fuel assembly emits very high radiation while in use in the reactor. To access the defective fuel rods it is necessary to remove the top and / or bottom nozzles of the fuel assembly. Typically, such nozzles are threadedly connected to the guided amble, or connected to the guided tack by means of a separate / groove device using a fixed tube as described in US Pat. No. 4,631,168.

Applicant's European Patent Publication No. A1-O 196 916 describes a reconfigurable fuel assembly having reusable fixation tubes with molded dimples. Some of the fasteners of such fuel assemblies have been found to be seated too low during reconstitution (to be seated too low means more than 0.76 mm from the top of the adapter plate of the top nozzle of the fastener). Investigations have shown that this problem can be attributed to two factors: if the seat is already seated too low from the installation and if the seat tube, which was initially seated properly, is seated too low due to the force generated by lifting or loading the fuel assembly from the core. It turns out to occur. Low seated stent tubes require special tools (longer tools) to remove such stent tubes when the fuel assemblies need to be rebuilt, making the task of underwater reconstruction more difficult.

The main object of the present invention is to reduce the accidental displacement of the fixed tube as described above.

Accordingly, the present invention (a) has an upper rim with a circumferential bulge projecting radially outward and defines an environmental recess in the interior of the rim, through the rim from the upper end of the tubular inner socket at an angled interval. A tubular inner socket defined by an upper end of the guide tumble, the plurality of elongated slots extending longitudinally; (b) a lower diameter upper portion, a larger diameter lower portion for slidingly receiving the portion of the inner socket comprising the upper rim, and a circumferential jaw formed between the upper and lower portions, An outer socket extending through the adapter plate forming part; The lower portion has an annular groove for receiving the circumferential bulge formed in the wall portion near the jaw, and (c) consists of a tubular body having a flexible wall with dimples protruding from the outer surface, the upper portion of the outer socket A holding tube that can slide through the portion into the inner socket; In the apparatus for detachably attaching the upper nozzle of the reconfigurable fuel assembly consisting of the upper portion of the guide dimple, wherein the dimple consists of at least one upper dimple and at least two lower dimples, the upper and lower dimples When the canister is in a fixed position pre-set in the inner socket, the tip of each upper dimple is positioned just below the jaw to prevent the rise of the canister with respect to the predetermined fastening position and the tip of each lower dimple is Arranged to be located just above the surface portion of the inner socket defining the lower edge portion of the recess to prevent the lowering of the fixation tube with respect to the pre-set fixing position, the lower dimple being defined between the plurality of long slots of the inner socket. It is specified that there is a predetermined angle of distance interval different from angle interval .

In particular, the tip of each upper dimple has a distance from the longitudinal centerline of the tubular body greater than the radius of the upper portion of the smaller diameter of the outer socket; The tip of each lower dimple is spaced from the longitudinal centerline of the tubular body by a distance greater than the difference between the radius of the lower diameter of the larger diameter of the outer socket and the wall thickness of the rim of the inner socket; The spacing between the upper and lower dimples is less than the distance present between the lowermost edge of the fold and the jaw when the circumferential bulge is inserted into the annular groove of the outer socket.

It is preferable that the fixed tube has an upper dimple and four lower dimples of thickness, and the four upper dimples are preferably disposed at points radially opposed to each other in an annular shape. In an apparatus in which the inner jacket has four long slots, the lower dimples are arranged in two pairs, each pair of lower dimples disposed at radially opposite points on the tubular body, and two pairs of lower dimples It is preferable to have a predetermined angle between 10 degrees and 45 degrees which is preferably 30 degrees. It is also preferable that the upper dimple is aligned in the longitudinal direction of one of the lower dimples of the two pairs and the fixed tube.

Preferred embodiments of the invention will now be described by way of example only with reference to the accompanying drawings.

First, referring to FIG. 1, which illustrates a typical fuel assembly 10 for a pressurized water raw material (PWR) in a vertically shortened form, the fuel assembly 10 uses the fuel assembly 10 as a lower core plate of the reactor core region. (Not shown) and a predetermined distance in the axial direction along the bottom nozzle 12, a plurality of guide tumble 14, longitudinally extending from the bottom nozzle 12, guide guide 14 A plurality of transverse lattice 16, a systematic arrangement of elongated fuel rods 18 supported laterally by a lattice 16 laterally, and an adapter plate 22 attached to an upper end of the guide drift 14. It consists of an upper nozzle (2). The guide tumble 14 is attached to the bottom nozzle 12 at its lower end. According to the component arrangement as described above, the fuel assembly 10 forms an integrated unit that can be conveniently handled without damaging the components of the assembly.

In particular, referring to FIG. 2 and FIG. 3, the upper nozzle guide tumble attachment device according to the present invention includes a control rod passage extending through the attenuator plate 22 of the upper nozzle 20 of the reconfigurable fuel assembly 10. Outer socket 26 defined as: an inner socket 36 constituting the upper end of each guide tumble 14; It consists of a fixed tube 24. It is particularly noted here that an attachment device as described and illustrated herein is provided for each guide tumble 14 to be attached to the top nozzle 20. The outer socket 26 has a relatively smaller diameter upper portion 28, a relatively larger diameter lower portion 30 having an annular groove 34 circumferentially formed in the wall of the socket, and an upper and lower portion. It has a jaw 32 formed between (28, 30).

Although the inner socket 36 is illustrated here as a sleeve bulged with the guided rim 14, it will be appreciated that it may instead be composed of an integrated top of the guidedumble itself. As can be seen from FIGS. 2 and 4, the inner socket 36 has an upper rim with a circumferential bulge 44 projecting radially outward, and the inner surface 46 of the circumferential bulge is annular at the inside of the rim. The recess 48 is defined. The inner socket 36 also forms a plurality of long slots 38 (four in the example embodiment) extending longitudinally from the upper end 42 of the inner socket through the rim including the circumferential bulge 44 have. The slots 38 are spaced at a predetermined angle from each other, and the socket wall portion therebetween defines a finger 40. As best seen from FIG. 5, the bottom or bottom edge of the recess 48 on each finger 40 begins to increase initially so that the inner diameter of the inner socket 36 yields the recess 48. , The point farthest from the upper end 42 of the inner socket. When the upper nozzle 20 is fixed on the guide tumble 14, the inner socket 36 has an upper end of the finger 40 positioned near the jaw 32 and an outwardly bulging rim 44 with a groove 34. Coaxially inserted into the outer socket 26 so as to be positioned horizontally. Upon insertion, the outward deflective flexible finger 40 of the inner socket 36 enters the shaved portion 54 by the inlet of the outer socket 26 and is elastically compressed at the same time, and the bulge rim 44 When mated with the annular groove 34 on the inner wall surface of the outer socket 26, it is elastically in its normal or expanded position.

As shown in FIGS. 6, 7 and 8, the fixation tube 24 is at least one embossed upper dimple 58 having a vertex or tip 60 at a predetermined angle from each other. It consists of a slidable tubular body 54 with a flexible wall having at least two embossed lower dimples 62 with a tip 64 thereon. When the upper nozzle 20 is attached to the guide tumble 14, that is, after each inner socket 36 is inserted into the associated outer socket 26, the fixed tube 24 is coaxially inserted into each inner socket 36. do. The dimples 58, 62 on the tubular body 56 of each fixation tube 24 are upper dimples 58 when the fixation tube 24 is in its proper securing position, as shown in FIG. Tip 60 of the inner socket 36, the tip 60 of the inner socket 36, the concave or recessed portion of the tip (64) of the lower dimple (62) 48) arranged in such a way that it is positioned at the position just above the lower edge 52. The tip 60 of the upper dimple 58 is also spaced apart from the longitudinal centerline of the tubular body 56 by a distance greater than the radius of the upper portion 28 of the outer socket 26, and is greater than that of the outer socket 26. It projects radially towards the lower portion 30 of larger diameter. This protruding type is made possible by selecting a suitable dimension for rim / groove engagement such that the upper end 42 of the inner socket is spaced apart from the jaw 32, or making the finger thickness smaller than the width of the jaw. In addition, the tip 64 of the lower dimple 62 on the fixed tube 24 provided is the difference between the radius of the lower portion 30 of the outer socket 26 and the thickness of some constant finger 40 (ie, the lower portion radius). Radially projecting from the longitudinal centerline of the tubular body 56 toward the recess 48 by a distance greater than the minus finger thickness). Finally, the lower dimple 62 is spaced at a predetermined angle so that when the lower dimple 62 is positioned in the slot 38, the other lower dimple 62 may contact the finger 40.

The fixed tube 24 is installed by inserting into the inner socket 36 through the upper portion of the outer socket 26 while applying sufficient force, and the inlet taper 66 formed at one end of the fixed tube is inserted into the fixed tube. To facilitate. When entering into the outer socket 26 of the fixed tube 24, the sleeve-shaped tubular body 56 is elastically stretched so that the dimples 58 and 62 can be inserted into the outer socket. It is important to note that the flexibility of the wall of the fixing tube is such that the wall is stretched when the fixed oil is removed while applying a predetermined force, but not under the force generated when the control rod or the tumble plug is withdrawn from the guide tumbler. . Once the fixation tube 24 reaches the appropriate seating depth in the outer and inner sockets, the upper dimple 58 will project radially outwardly under the jaw 32 and at least one of the lower dimples 62 will have a finger 40 Will radially outward into the recess or recess 48. In installation, the fact that the above conditions have been reached is indicated by the increase in force required to move the fixation tube 24 up and down in the axial direction, which may occur if the fixation tube is properly seated. By projecting the dimple tip a distance as defined above and keeping the gap between the upper and lower dimples less than the distance present between the bottom edge 52 of the recess 48 and the jaw 32, the bulge 44 ) Is inserted into the groove 34 of the outer socket, the upper dimple 58 will engage the passage, or the jaw 32 of the outer socket 28 with sufficient force, to prevent accidental lifting of the fixation tube 24, At least one of the lower dimples 62 horizontally engages the fingers with sufficient force at the lowermost edge 52 of the recess 34 to prevent accidental lowering of the securing tube 24 relative to the adapter plate 22. To be aligned with the finger 40. The fixed tube 24 inserted into the inner socket 36 prevents accidental movement of the outward bulge rim 44 of the finger 40 with respect to the annular groove 34 in the outer socket 26, thereby guiding the guide tumble ( It will prevent accidental departure of the upper nozzle 20 to 14). If it is necessary to remove the fixing tube so that the upper nozzle can be removed, the fixing tube 24 may be stretched to release the fixing tube 24 from the sockets 26 and 36, so that each fixing tube may be overcome. Apply sufficient force in the axial direction with respect to (24).

Dimples 58, 62 may be formed by internal / external die operations that are well known to those skilled in the art. The fixed tube 24 preferably has two upper dimples 58 (FIG. 7) and four lower dimples 62 (FIG. 8). In order to help elastically stretch the sleeved tube 56 during installation and removal of the fixed tube 24, the lower dimples 62 are two dimples diametrically opposed to each other as shown in FIG. Two pairs of pairs (62) are formed, and the two pairs of the lower dimples have a predetermined angle between 10 degrees and 45 degrees where 30 degrees are preferable to each other. Similarly, the upper dimples 58 are arranged radially to each other, as can be seen from the seventh degree, and the pair of upper dimples 58 is one of two pairs of the lower dimples 62 and the axis (vertical axis of the fixing tube). Direction) (see Figure 6).

The fixed tube 24 is typically made of stainless steel having a length of 3.18 cm, an inner diameter of 1.15 cm and a wall thickness of 0,4 mm. The dimples 58, 62 generally form a square base with 0.6 mm on each side and a diamond of 0.3 mm height at the tip 60, or 64. The upper dimple 58 typically has a spacing of 3.3 mm from the top of the fixed tube 24 and 2.8 mm from the lower dimple 62.

Claims (7)

(a) having an upper rim with a circumferential bulge 44 projecting radially outwardly defining an annular recess 48 on the inside of the rim, the upper part from the upper end of the tubular inner socket at predetermined angles; A tubular inner socket 36 defined as an upper end of the guide tumble 14 forming a plurality of long slots 38 extending longitudinally through the rim; (b) a smaller diameter upper portion 28, a larger diameter lower portion 30 for slidingly receiving the portion of the inner socket comprising the upper rim, and upper and lower portions 28 and 30; An outer socket 26 having a circumferential jaw 32 formed therebetween and extending through an adapter plate 22 forming a part of the upper nozzle 20; (C) a flexible wall having dimples protruding from an outer surface of said lower portion 30 for receiving said columnar paper 44 formed in the wall portion near said jaw 32; A tubular body 56 having a fixed tube 24 which can be slid into the inner socket 36 through the upper portion 28 of the outer socket 26; A device for removably attaching an upper nozzle of a reconfigurable fuel assembly to a top end of a guide dimple, wherein the dimple comprises at least one upper dimple 58 and at least two lower dimples 62. And the upper and lower dimples are lifted in the fixed tube with respect to the fixed position in which the tip 60 of each upper dimple 58 is in the predetermined fixed position when the fixed tube 24 is in the predetermined fixed position in the inner socket 36. The lower edge portion of the recess 48 so that the tip 64 of each lower dimple 62 prevents the lowering of the fixation tube with respect to the predetermined fixing position. The lower dimple 62 is arranged to be positioned directly above the surface portion of the inner socket 36 defining a distance between the plurality of long slots 38 of the inner socket 36 and at a different distance from the predetermined angle. A predetermined interval A reconfigurable top nozzle of the fuel assembly, characterized in that with the apparatus is also able to be attached removable to the upper end of the guide dimbeul. The tip 60 of each of the upper dimples 58 according to claim 1, wherein the tip 60 of the upper dimple 58 is smaller than the radius of the smaller diameter upper portion 28 of the outer socket 26 from the longitudinal center line of the tubular body 56. At large distances; The tip 64 of each of the lower dimples 62 has a radius of the lower portion 30 of the larger diameter of the outer socket 26 and the radius of the inner socket 36 from the longitudinal centerline of the tubular body 56. Spaced by a distance greater than the difference between the wall thicknesses of the rims; The gap between the upper and lower dimples 58, 62 is such that the lower edge 34 of the recess 48 and the jaw (when inserting the bulge bulge 44 into the annular groove 34 of the outer socket 26). 32. A device for removably attaching the upper nozzle of the reconfigurable fuel assembly to the upper end of the guide tumbler, characterized in that it is smaller than the distance present between. The upper nozzle of the reconfigurable fuel assembly according to claim 1 or 2, wherein the fixed tube (24) has two upper dimples (58) and four lower dimples (62). Detachable device for attaching to the upper end of the. 4. The upper nozzle of the reconfigurable fuel assembly according to claim 3, wherein the four upper dimples (58) are disposed at diametrically opposed points on the tubular body (56) at the upper end of the guide dimple. Device for secure attachment. 5. The inner socket 36 has four long slots 38, the lower dimples 62 arranged in two pairs, and each pair of lower dimples 62 is the tubular body. The upper nozzle of the reconfigurable fuel assembly is disposed at a point facing each other in diameter on the 56, and the two pairs of the lower dimples 62 have a predetermined angle between 10 and 45 degrees from each other. Device for attaching detachably to the upper part. 6. The apparatus of claim 5 wherein the two pairs of lower dimples (62) are at an angle of 30 degrees to each other. 7. The reconfigurable fuel assembly according to claim 5 or 6, wherein the upper dimple (58) is aligned in the longitudinal direction of one of the two lower dimples (62) and the fixed tube (24). Apparatus for attaching the upper nozzle of the guide thimble detachably.

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